Feline and canine coronaviruses (FCoV and CCoV) exhibit a very close antigenic relationship which makes interspecies transmission possible. Following such interspecies infections recombinations may occur in various regions of the viral genome. The aim of our study was to get more information about phylogenetic relationships between canine and feline coronavirus field isolates originating from animals with intensive contact possibilities between these species.

Faecal samples of 12 cats and 10 dogs living in an animal shelter and previously diagnosed as coronavirus positive were submitted to sequence and phylogenetic analyses. Amplification products obtained with the primers CCoV1 and CCoV2 amplifying 409 bp of the M gene (Pratelli et al., 2000) were sequenced and aligned with other feline, canine and porcine sequences from the GenBank.

Nucleotide alignments of the CCoV field isolates revealed clearly at least two different types of CCoV. Three of the 10 canine samples showed a homology of 93-96 % with classical CCoV strains; however, a second CCoV type, comprising the remaining seven canine samples, showed homologies of only 86-91 % with the classical strains but of 96-98 % with the FCoV-like isolate recently described by Pratelli and coworkers. Surprisingly, similar as in canine isolates, at least two different genetic clusters were present in feline field isolates as well. The first cluster was to 92-95 % identical with classical FCoV strains and only to 78-86 % with classical CCoV strains. The second cluster of feline isolates was more closely related to the atypical CCoV strain (86-88 %) than to any FCoV strain (81-85 %).

Our results confirm the description of two different clusters of CCoV circulating in the field. The detection of at least two genetic clusters of FCoV in cats, one species specific, the other more closely related to CCoV, was not yet published to our knowledge. Our results underline the possibility that interspecies transmissions of coronaviruses between dogs and cats may occur frequently resulting in recombination events. The clinical aspects of these new types need further investigations. The question arises whether these new atypical feline isolates are of any clinical importance as the atypical CCoV isolates are believed to be.

Reference

1.  Pratelli, A. et al. (2000), J. Virol. Meth. 106, 209 - 213.